Unless all things are identical the variables to compare one vehicle to the next on sound levels the value may be to that owner only. Type of measure tool, placement, ambient noise HVAC, road conditions, state where tested, tires, sunroof, sound proofing material used, how it's attached, etc.
Consider moving, with a assistance, the sound meter being used to locate the root cause(s) which may be the first area to focus on and depending on how much difference is noticed after applying material the need to do the entire vehicle may not be required for some individuals.